Colon cancer is the third leading cause of cancer related mortality in the United States. Studies indicate that approximately 57,000 people died due to colon cancer in 2003 in the United States alone. With the removal of abnormal growths or polyps, which are a pre-cancerous stage of colon cancer, a patient has a 90% chance of survival 5 years after the removal.
The accepted standard for screening colon cancer is colonoscopy. However, colonoscopy is an invasive test, and hence has a low acceptance probability among patients. Computed tomography (CT) colonography is a test for screening for colon cancer using CT scanning. CT colonography involves minimal invasion. However, the sensitivity of CT colonography is lower than that of colonoscopy.
There exist advanced methods to increase the sensitivity of colonography. One method involves a fly-through three-dimensional visualization of a segmented colon using volume rendering techniques. Another method involves rendering and studying a virtually dissected colon. This method is described in a paper titled “Virtual Colon Unfolding” by Bartroli et al., published as a part of the IEEE proceedings on Visualization in 2001. Both these methods rely on mapping intensity values obtained from a CT scanner to a volume rendered three-dimensional view.
The presence of fecal matter in a colon can obstruct the visualization of anatomical details within such three dimensional views. Fecal matter acts as a source of false positives as it visually resembles abnormal growths within the colon. Hence, the removal of fecal matter from a CT image of a colon leads to an increase in the sensitivity of CT colonography.